Process for making HIV protease inhibitors

ABSTRACT

Intermediates of structural formula ##STR1## can be made by reacting a primary or secondary amine with glycosidol or an activated derivative thereof. The process and intermediates are useful for synthesizing HIV protease inhibitor compounds.

This application is a divisional application of Merck Case 19045DA, U.S.Ser. No. 08/341,334, filed Dec. 16, 1994, abandoned, which is acontinuation of Merck Case 19045, U.S. Ser. No. 08/092,627, filed Jul.16, 1993, abandoned.

BACKGROUND OF THE INVENTION

The present invention is concerned with a novel intermediate and processfor synthesizing compounds which inhibit the protease encoded by humanimmunodeficiency virus (HIV), and in particular L-735,524, orpharmaceutically acceptable salts thereof. These compounds are of valuein the prevention of infection by HIV, the treatment of infection by HIVand the treatment of the resulting acquired immune deficiency syndrome(AIDS).

More specifically, the instant process involves the reaction of an aminenucleophile such as a piperazine derivative, with an activated glycidylderivative such as 2(S)-glycidyl nosylate, to afford an epoxideintermediate which is useful in the preparation of HIV proteaseinhibitor compounds, including L-735,524. Also provided is an improvedprocess for the synthesis of specific dialkylamines used in thesynthesis of HIV protease inhibitors.

A retrovirus designated human immunodeficiency virus (HIV) is theetiological agent of the complex disease that includes progressivedestruction of the immune system (acquired immune deficiency syndrome;AIDS) and degeneration of the central and peripheral nervous system.This virus was previously known as LAV, HTLV-III, or ARV. A commonfeature of retrovirus replication is the extensive post-translationalprocessing of precursor polyproteins by a virally encoded protease togenerate mature viral proteins required for virus assembly and function.Inhibition of this processing prevents the production of normallyinfectious virus. For example, Kohl, N. E. et al., Proc. Nat'l Acad.Sci. 85, 4686 (1988) demonstrated that genetic inactivation of the HIVencoded protease resulted in the production of immature, non-infectiousvirus particles. These results indicate that inhibition of the HIVprotease represents a viable method for the treatment of AIDS and theprevention or treatment of infection by HIV.

The nucleotide sequence of HIV shows the presence of a pol gene in oneopen reading frame [Ratner, L. et al., Nature, 313, 277(1985)]. Aminoacid sequence homology provides evidence that the pol sequence encodesreverse transcriptase, an endonuclease and an HIV protease [Toh, H. etal., EMBO J. 4, 1267 (1985); Power, M. D. et al., Science, 231, 1567(1986); Pearl, L. H. et al., Nature 329, 351 (1987)]. The end productcompounds, including L-735,524 which is shown in Example 11 below, thatcan be made from the novel intermediates and processes of this inventionare inhibitors of HIV protease, and are disclosed in EPO 541,168, whichpublished on May 12, 1993.

Previously, the synthesis of L-735,524 and related compounds wasaccomplished via a 12-step procedure which employed a hydroxy protecteddihydro-5(S)-hydroxymethyl-3(2H)-furanone which was alkylated, andinvolved replacement of an alcohol leaving group on the alkylatedfuranone with a piperidine moiety. The coupled product was thenhydrolyzed to open the furanone ring into a hydroxy acid moiety, and theacid was ultimately coupled to 2(R)-hydroxy-1(S)-aminoindane. Thisprocedure is described in EPO 541,168. The extreme length of this route(12 steps), renders this process time consuming and labor intensive, andit requires the use of many expensive reagents and an expensive startingmaterial. A route requiting fewer reaction steps and reagents wouldprovide desirable economical and time-saving benefits.

A modified route to L-735,524 and related compounds was also shown inEPO 541,168 based on the diastereoselective alkylation of the enolatederived fromN-(2CR)-hydroxy-1(S)-indan-N,O-isopropylidene-yl)-3-phenyl-propaneamide,in which the C₃ -C₅ three-carbon unit was introduced as an allyl groupand later oxidized. Some problems with this route are: (a) four stepsare necessary to effect the introduction of the three carbon glycidylfragment, (b) highly toxic OsO₄ is used in the process and (c) lowdiastereoselectivity is obtained in the dihydroxylation step. Thus, adesirable process would directly introduce the three carbon unit in thecorrect chiral oxidized form.

Furthermore, the synthesis of the chiral piperazine intermediate waseffected from 2-pyrazinecarboxylic acid in a 6 step procedure andrequired the use of expensive reagents such as BOC-ON and EDC. A shorterroute to the piperazine intermediate which also does not use expensivereagents would thus be desired.

Several examples of condensations of stabilized carbanions with glycidoland its derivatives (activated or unactivated) are known in theliterature; however, no known methods produce a new epoxide directly ingood yield. See, e.g., Hanson, R. M., Chem. Rev., 1991, 91, 437-475. Inthe case of activated glycidol derivatives and carbon nucleophiles, thisis due primarily to the anticipated and undesirable "double" addition ofthe nucleophile to the epoxide product.

Condensations of stabilized carbanions with activated non-racemicglycidol derivatives have been demonstrated: malonate anion has beencoupled with both non-racemic epichlorohydrin i and non-racemic glycidyltriflate ii to afford the cyclopropyl-lactone ii. See, e.g., Pirrung, M.C., et al., Helvetica Chimica Acta 1989, 72, 1301-1310, and Burgess, K.,et al., J. Org. Chem. 1992, 57, 5931-5936. Thus, in this case, theintermediate epoxide undergoes further reaction to afford thecyclopropyl ring system. In the case of i, the initial reaction withmalonate anion occurs at the epoxide terminus (C₃), whereas with ii, theinitial reaction occurs at the triflate C₁ terminus. ##STR2##

A related example is reaction of sulfone-stabilized carbanion derivedfrom v with glycidyl tosylate iv to afford the hydroxy-tosylate vi. See,e.g., Baldwin, J. E., et al., J. Chem. Soc. Chem. Commun. 1992,1249-1251. In this case, although double addition of the carbanion isnot a major problem, an additional step is necessary to convert theintermediate hydroxy-tosylate vi to the desired epoxide vii. ##STR3##

Similarly, it is unknown in the literature and unexpected that nitrogennucleophiles can be selectively added to activated glycidol derivativesin good yield without the problematic double addition.

Also known in the art is the condensation of amide enolates derived fromN-(2(R)-hydroxy-1(S)-indan-N,O-isopropylidene-yl)-3-phenylpropaneamide 7with protected alpha-amino epoxides viii to afford the desiredhydroxyethylene dipeptide isostere intermediates ix with a high degreeof stereocontrol for the C₂ -(R)-stereocenter. See, e.g., Askin, D., etal., J. Org. Chem., 1992, 57, 2771-2773 and U.S. Pat. No. 5,169,952 toAskin, D., et al. After hydrolysis, the deprotected hydroxyethylenedipeptide isostere inhibitors are obtained. ##STR4##

The resolution of 2-piperazinecarboxylic acid with (+)-CSA is known.See. e.g., Felder, E., et al., Helvetica Chim. Acta, 1960, 43, 888.However, examples of the resolution of piperazine amides are not knownin the literature.

The instant invention provides a more advantageous method for preparingHIV protease inhibitors than previously known. It allows a much shorter,more highly diastereoselective, higher yielding synthesis of thecompounds disclosed in EPO 541,168, and in particular L-735,524, withoutthe use of toxic reagents such as osmium tetraoxide or expensivereagents such as (S)-(+)-dihydro-5-(hydroxy-methyl)-2(3H)-furanone.

SUMMARY OF THE INVENTION

The instant invention involves novel synthetic methods for makingamino-epoxide intermediates such as 3, which are useful for thesynthesis of HIV protease inhibitors. One embodiment of the inventioninvolves the reaction of an amine nucleophile such as 1 with anactivated glycidol derivative such as 2(S)-glycidyl nosylate 2, toafford an epoxide product such as 3 in good yield. The result of thisreaction is unexpected since epoxide 3 was predicted to undergo furtherreaction under the coupling conditions to afford a large amount of dimerproduct 3-a, thus giving poor yields of 3. ##STR5##

Another embodiment of the instant invention involves reacting the aminenucleophile with non-racemic glycidol, followed by treatment with tosylchloride (TsCl) then base to obtain the amino-epoxide intermediate.

Still another embodiment involves the reaction of the amino-epoxideintermediate with an amide of formula VIII, defined below, to produceintermediates of formula I, defined below.

A further embodiment of the instant invention involves novel routes forobtaining compound 1 in the desired chiral configuration. This can beaccomplished efficiently and in high yield by treatment of racemic2-tert-butyl-carboxamide piperizine with (+)-CSA or L-PGA followed bycrystallization of the chiral product, which is then protected with BOC₂O. Alternatively, the compound 1 is obtained by kinetic methods.

Some abbreviations that may appear in this application are as follows.

    ______________________________________                                        ABBREVIATIONS                                                                 ______________________________________                                        Designation  Protecting Group                                                 BOC (Boc)    t-butyloxycarbonyl                                               CBZ (Cbz)    benzyloxycarbonyl (carbobenzoxy)                                 TBS (TBDMS)  t-butyl-dimethylsiyl                                             Designation  Activating Group                                                 Ts or tosyl or tosylate                                                                    p-toluenesulfonyl                                                Ns or nosyl or                                                                             3-nitrobenzenesulfonyl                                           nosylate                                                                      Tf or triflyl or triflate                                                                  trifluoromethanesulfonyl                                         Ms or mesyl or                                                                             methanesulfonyl                                                  mesylate                                                                      Designation  Coupling Reagent                                                 BOP reagent  benzotriazol-1-yloxytris(dimethylamino)-                                      phosphonium hexafluorophosphate                                  BOP-Cl       bis(2-oxo-3-oxazolidinyl)phosphinic                                           chloride                                                         EDC          1-ethyl-3-(3-dimethylaminopropyl)                                             carbodiimide hydrochloride                                                    Other                                                            BOC-ON       2-(tert-butylcarbonyloxyimino)-                                               2-phenylacetonitrile                                             (BOC).sub.2 O (BOC.sub.2 O or                                                              di-t-butyl dicarbonate                                           Boc.sub.2 O)                                                                  n-Bu.sub.4 N.sup.+ F.sup.-                                                                 tetrabutyl ammonium fluoride                                     nBuLi (n-Buli)                                                                             n-butyllithium                                                   (S)-CSA      (1S)-(+)-10-camphorsulfonic                                                   acid                                                             DIEA or DIPEA                                                                              diisopropylethylamine                                            DMAP         dimethylaminopyridine                                            DME          dimethoxyethane                                                  DMF          dimethylformamide                                                Et.sub.3 N   triethylamine                                                    EtOAc        ethyl acetate                                                    h            hour(s)                                                          IPA          2-propanol                                                       LDA          lithium diisopropylamide                                         L-PGA        (L)-pyroglutamic acid                                            TFA          trifluoroacetic acid                                             THF          tetrahydrofuran                                                  TLC          thin layer chromatography                                        ______________________________________                                    

DETAILED DESCRIPTION OF THE INVENTION

The instant invention provides a novel process for making intermediatesof formulas I and II which are useful in the preparation of HIV proteaseinhibitors, and in particular those compounds disclosed in EP0 541,168.The process for making intermediates of formula I ##STR6## comprises thesteps of: (1) producing a compound of formula II ##STR7## by reacting anamine of formula III ##STR8## with either: (a) a glycidol of formula IV##STR9## in the presence of base, or with (b) a glycidol of formula V##STR10## to produce a compound of formula VI ##STR11## treating VI withan activating agent selected from the group consisting ofp-toluenesulfonyl chloride (also known as tosyl chloride or TsCl),methanesulfonyl chloride (also known as mesyl chloride or MsCl),trifluoromethanesulfonic anhydride (also known as triflic anhydride orTf₂ O) and PBr₃ to produce VII ##STR12## and treating VII with a strongbase to obtain II; and (2) reacting II an amide of formula VIII##STR13## in the presence of a strong base at a low temperature;wherein:

stereocenter a is in either the R configuration, the S configuration oris racemic;

r is an integer from zero through and including 5;

G is a group selected from 3-nitrobenzenesulfonyl andtrifluoromethanesulfonyl;

X is a group selected from p-toluenesulfonyl, methanesulfonyl, andtrifluoromethanesulfonyl;

R¹ and R² are independently selected at each occurrence from the groupconsisting of:

1) hydrogen,

2) --C₁₋₄ alkyl unsubstituted or substituted with one or more of

a) hydroxy,

b) C₁₋₃ alkoxy,

c) aryl unsubstituted or substituted with one or more of C₁₋₄ alkyl,hydroxy or aryl,

d) --W-aryl or --W-benzyl, wherein W is --O--, or --S--,

e) a 5-7 membered cycloalkyl group unsubstituted or substituted with oneor more of

i) hydroxy,

ii) C₁₋₃ alkoxy, or

iii) aryl,

f) heterocycle unsubstituted or substituted with one or more of hydroxy,C₁₋₄ alkyl, C₁₋₄ alkyl substituted with hydroxy, or Boc,

g) --NH--COOC₁₋₃ alkyl,

h) --NH--CO--C₁₋₃ alkyl,

i) --NH--SO₂ C₁₋₃ alkyl,

j) --COOR, or

k) --((CH₂)_(m) O)_(n) R, or

3) aryl, unsubstituted or substituted with one or more of

a) halo,

b) hydroxy,

c) --NO₂ or --N(R)₂,

d) C₁₋₄ alkyl,

e) C₁₋₃ alkoxy, unsubstituted or substituted with one or more of --OH orC₁₋₃ alkoxy,

f) --COOR,

g) --CON(R)₂,

h) --CH₂ N(R)₂,

i) --CH₂ NHCOR,

j) --CN,

k) --CF₃,

l) --NHCOR,

m) aryl C₁₋₃ alkoxy,

n) aryl,

o) --NRSO₂ R,

p) --OP(O)(OR_(x))₂, or

q) -R⁵, as defined below; or

R¹ and R² can be joined together with the nitrogen to which R¹ isattached and the carbon to which R² is attached to form a 3 to 10membered monocyclic or bicyclic saturated ring system which consists ofthe nitrogen to which R¹ is attached and from 2 to 9 carbon atoms suchas, for example, ##STR14## and is unsubstituted or substituted with oneor more of: 1) hydroxy,

2) C₁₋₄ alkyl unsubstituted or substituted with one or more of

a) halo,

b) hydroxy,

c) C₁₋₃ alkoxy,

d) aryl,

e) a 5-7 membered cycloalkyl group unsubstituted or substituted with oneor more of

i) hydroxy,

ii) C₁₋₃ alkoxy, or

iii) aryl, or

f) heterocycle,

3) C₁₋₃ alkoxy,

4) --NH--COOC₁₋₃ alkyl,

5) --NH--CO--C₁₋₃ alkyl,

6) --NH--SO₂ C₁₋₃ alkyl,

7) heterocycle,

8) --W-aryl, or

9) --W--CO-aryl,

wherein W is defined above; or

R¹ and R² can be joined together with the nitrogen to which R¹ isattached and the carbon to which R² is attached to form a 3 to 10membered monocyclic or bicyclic saturated ring system which consists ofthe nitrogen to which R¹ is attached, from 1 to 8 carbon atoms and oneor more unsubstituted or substituted heteroatom selected from

1) ##STR15## wherein V is absent or --CO--Q-- or --SO₂ --Q--, R¹ isdefined as above for when R¹ is independent from and not joined to R²,

and wherein Q is absent or --O--, --NR--, or heterocycle optionallysubstituted with --C₁₋₄ alkyl,

2) ##STR16## 3) ##STR17## unsubstituted or substituted with aryl, 4)##STR18## unsubstituted or substituted with aryl, 5) --S(O)_(p) --,wherein p is zero, 1 or 2, or

6) --O--,

such as, for example, ##STR19## R³ is selected from the group consistingof: 1 ) hydrogen,

2) --C₁₋₄ alkyl

3) C₅ -C₁₀ cycloalkyl, optionally substituted with hydroxy,

4) C₆ -C₁₀ aryl, unsubstituted or substituted with one or more of:

a) halo,

b) hydroxy,

c) --NO₂ or --N(R)₂,

d) C₁₋₄ alkyl,

e) C₁₋₃ alkoxy, unsubstituted or substituted with one or more of --OH orC₁₋₃ alkoxy,

f) --COOR,

g) --CON(R)₂,

h) --CH₂ NCR)₂,

i) --CH₂ NHCOR,

j) --CN,

k) --CF₃,

l) --NHCOR,

m) aryl C₁₋₃ alkoxy,

n) aryl,

o) --NRSO₂ R,

p) --OP(O)(OR_(x))₂, or

q) --R⁵, as defined below, or

5) monocyclic or bicyclic heterocycle containing from 1 to 3 heteroatomschosen from the group consisting of N, O, and S, such as, for example,2-pyridyl, 3-pyridyl, or 4-pyridyl, and which is unsubstituted orsubstituted with R⁵ and optionally with one or more of

a) halo,

b) C₁₋₄ alkyl, or

c) C₁₋₃ alkoxy;

m is 2, 3, 4 or 5;

n is zero, 1, 2 or 3;

R is hydrogen or C₁₋₄ alkyl;

R_(x) is H or aryl;

R⁴ is C₁₋₅ alkyl, straight or branched chain; and

R⁵ is

1) --W--(CH₂)_(m) --NR⁶ R⁷ wherein W and m are defined above, and R⁶ andR⁷ are independently selected at each occurrence from:

a) hydrogen,

b) C₁₋₆ alkyl, unsubstituted or substituted with one or more of

i) C₁₋₃ alkoxy,

ii) --OH, or

iii) --N(R)₂,

c) aromatic heterocycle unsubstituted or substituted with one or more of

i) C₁₋₄ alkyl, or

ii) --N(R)₂,

d) or R⁶ and R⁷ are joined together with the nitrogen to which they areattached to form a 5-7 member heterocycle, such as morpholino,containing up to two additional heteroatoms selected from --N(R), --O--,--S--, --S(O)-- or --S(O)₂ --, the heterocycle optionally substitutedwith C₁₋₄ alkyl,

2) --(CH₂)_(q) --NR⁶ R⁷ wherein q is an integer from 1-5, and R⁶ and R⁷are defined above, except that R⁶ or R⁷ are not H or unsubstituted C₁₋₆alkyl, or

3) benzofuryl, indolyl, azacycloalkyl, azabicyclo C₇₋₁₁ cycloalkyl, orbenzopiperidinyl, unsubstituted or substituted with C₁₋₄ alkyl.

Schemes 1 and 2 below illustrate this process. However, the instantprocess is not limited by any particular substituents employed in theschemes which are used for the purpose of illustration. ##STR20##

A suitable group may be used to activate glycidol IV, such as, e.g.,3-nitrobenzenesulfonyl or trifluoromethanesulfonyl, with3-nitrobenzenesulfonyl being preferred. Any suitable polar solvent maybe used for the reaction of III with IV such as e.g., dimethylformamide(DMF), N-methyl pyrrolidinone, acetone, butanone, acetonitrile,tert-butyl alcohol, tert-amyl alcohol, 2-propanol, N-ethylpyrrolidinone, 1,1,3,3-tetramethylurea, dimethylsulfoxide,1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, tetramethylsulfone,tetrahydrofuran (THF), 1,4-dioxane, pyridine and water, and combinationsthereof. The preferred polar solvents are DMF, N-methylpyrrolidinone,acetone, 2-butanone and acetonitrile, with DMF being most preferred. Anysuitable base may be used for the reaction of III with IV, and suchbases include, e.g., diisopropylethylamine (DIEA), potassium carbonate,sodium carbonate, sodium bicarbonate, triethylamine, pyridine, anddimethylaniline; DIEA and potassium carbonate are preferred, with DIEAbeing most preferred. Preferably, about 1:1 molar equivalents of III:IVare used in this reaction step. The reaction is preferably run at anelevated temperature, for example in the range of about 50° C. to 70°C., with about 60° C. to 65° C. being more preferred.

Glycidol V is reacted with amine III in a ratio of about 1-3 molarequivalents of V per one mole of III, with a molar equivalent ratio ofabout 1.5:1 of V:III being preferred, in a suitable solvent. Suitablesolvents include, e.g. hydrocarbons, ethers such as di-ethyl ether,alcohols such as methanol, ethanol, or isopropanol, nitriles such asacetonitrile, and esters such as ethyl acetate or combinations thereof,with alcohols being preferred. The reaction may be run at a temperaturebetween ambient temperature and the reflux temperature of the solventused, with an elevated temperature preferred. Most preferably, thesolvent is isopropanol and the reaction is run at about 85° C.

The hydroxy group of VI is activated to form VII using standardtechniques known to those in the art. From about 1 to 3 molarequivalents of TsCl, MsCl, or Tf₂ O per molar equivalent of VI can beused for this purpose, with a ratio of about 1.5:1 molar equivalents ofactivating agent:VI preferred. X is preferably p-toluenesulfonyl, andtherefore TsCl is preferred for this step. The reaction is preferablyrun at ambient temperature, i.e., about 25° C., but it can be run at alower or higher temperature such as from -20° to 80° C. Any suitablesolvent known to those skilled in the art may be used in this step, suchas e.g., hydrocarbons, ethers, nitriles, esters, and amines such aspyridine or combinations thereof. Pyridine is most preferred as thesolvent. It is preferable not to use an alcoholic solvent.

The activated intermediate VII is finally treated with a strong basepreferably at room temperature to form II, although the reaction may berun at lower and higher temperatures as from 0° C. to the refluxtemperature of the solvent used. Suitable strong bases include NaH,KOC(CH₃)₃, KOC(CH₃)₂ CH₂ CH₃, NaOC(CH₃)₂ CH₂ CH₃, lithiumdiisopropylamide (LDA), n-butyllithium (n-BuLi), lithiumbis(trimethylsilyl)amide or a similar strong base known in the art, andNaH is preferred. About 1 to 3 molar equivalents of base is generallyused per molar equivalent of VII, with a ratio of 1.5:1 molarequivalents of base:VII being preferred. Any suitable solvents can beused in this step, such as, e.g., hydrocarbons, ethers, nitriles, andesters or combinations thereof, with THF being the preferred solvent. Itis preferable not to use an alcoholic solvent.

Intermediates VIII and II are coupled using a strong base in an etherialsolvent. The strong base must be a metal-containing base. The strongbase may or may not be in an inert anhydrous organic solvent, such as,e.g., cyclic or acyclic hydrocarbons including hexane, pentane,cyclohexane, etc. Suitable strong bases include: n-butyllithium(n-BuLi), s-BuLi, t-BuLi, lithium diisopropylamide (LDA), lithiumisopropylcyclohexylamide, lithium pyrrolidide, lithiumtetramethylpiperidide, phenyllithium, isopropylmagnesium chloride,isobutylmagnesium chloride, and other similar strong bases known in theart. Preferred strong bases are n-BuLi, s-BuLi, and LDA, with n-BuLibeing most preferred. About 1 to 2 molar equivalents of base can be usedper molar equivalent of VIII; preferably, 1.05 to 1.2 molar equivalentsand most preferably 1.15 molar equivalents of base are used per molarequivalent of VIII. The reaction of VIII with II can be done bycombining VIII and II in one pot and then adding the strong base, or itcan be done sequentially, i.e., by first treating amine VIII with basefollowed by addition of II.

The strong base effects metalation of the amide VIII at the positionalpha to the carbonyl group to afford the reactive metal amide enolatewhich then effects ring opening of the epoxide II at the terminalposition to afford compound I. A new center of asymmetry is created inthe product isostere I at the 2-position.

The reaction is preferably run at a low temperature, for example rangingbetween about -82° C. and 0° C. To effect metalation of the amide VIII,the temperature range is maintained more preferably between about -82°C. and -40° C. and most preferably between about -50° C. and -45° C. Toeffect the reaction of the metalated amide derivative of VIII and theglycidol derivative II to form I, the temperature range is maintainedmore preferably between about -50° C. and -10° C., and most preferablybetween about -30° C. to -20° C. for about 4-5 hours, although thelength of the reaction may vary depending on the reaction scale andother factors known to those skilled in the art.

The etherial solvents are any solvents suitable for use in this couplingstep including, e.g., THF, 1,2-dimethoxyethane, di-ethyl ether andmethyl-t-butyl ether, with THF being preferred.

Activated glycidols of formula IV can be prepared by methods known inthe art, such as described in, e.g., J. Klunder, et al., J. Org. Chem.,1989, 54, 1295-1304 and references cited therein.

Compounds of formula VIII can be made according to standard proceduresknown to those skilled in the art, such as, e.g., the proceduredescribed in Example 1, using the appropriate starting materials.

Protecting groups such as nitrogen protecting groups may be used whereappropriate in the practice of this invention. For example, the 4position nitrogen of 2-t-butylcarboxamide piperazine may be protectedwith a group such as BOC, CBZ, benzyl, 4-methoxybenzyl,2,4-dimethoxybenzyl, trifluoroacetamide, trialkylsilyl, or other groupsknown in the art.

End-product HIV protease inhibitors are made from compounds of formula Iby removing any remaining protecting groups present according todeprotection methods well known to those skilled in the art. Forexample, the ketal protecting group can be removed by treating I withacid in the presence of methanol, or by aqueous acid or by 1N HCl inTHF, to produce the final HIV protease inhibitor products. Compounds offormula I may also be further substituted by methods known in the art.

In one embodiment of this invention, stereocenter a has the Sconfiguration; r is 1; G is 3-nitrobenzenesulfonyl; X isp-toluenesulfonyl; R¹ and R² are joined together to form a cyclicstructure selected from the group consisting of: ##STR21## R³ isselected from phenyl, ##STR22## R⁴ is tert-butyl.

Within this embodiment is the preferred species of formula II which isthe intermediate compound of formula II-a ##STR23##

Also within this embodiment are the preferred species of formula I,which are the intermediate compounds of formulas I-a and I-b ##STR24##

Compound I-b can be made by directly coupling the 4N-methylpyridylderivative of II-a with the appropriate species of formula VIII.Preferably, the final product L-735,524 is made by deprotection andpicolylation of I-a, as exemplified in Examples 10-11.

Another embodiment of this invention involves the preparation of thechiral intermediate(S)-2-tert-butylcarboxamide-4-tert-butoxycarbonylpiperazine 1. Compound1 is obtained by treatment of a salt form of(S)-2-tert-butylcarboxamidepiperazine with base followed by Boc₂ O.Nitrogen protecting groups other than Boc, such as CBZ, benzyl, etc.,may also be used.

The formation and resolution of the salt form of(S)-2-tert-butylcarboxamidepiperazine is accomplished by a novel processcomprising the steps of:

(a) contacting a solution of (S)(R)-2-tert-butylcarboxamide-piperazinewith an acid in an aqueous-organic solvent mixture, wherein the acid isselected from the group consisting of (+) or (-) tartaric acid, (+) or(-) mandelic acid, (+) or (-) dibenzoyltartaric acid, D orL-pyroglutamic acid (also known as (+) or (-) 2-pyrrolidine-5-carboxylicacid), (+) or (-) di-O,O'-p-toluyl-tartaric acid, (+) or (-)-malic acid,(+) or (-)-10-camphorsulfonic acid (+) or (-)-3-bromo-10-camphorsulfonicacid, and (+) or (-)-3-chloro-10-camphorsulfonic acid;

(b) heating the mixture to dissolve any solid that forms;

(c) cooling the mixture;

(d) separating the precipitated crystals from the mother liquor; and

(e) if the mother liquor is predominantly comprised of the (S)-antipode,removing the solvent therefrom.

The organic solvents suitable for the resolution process include, e.g.,water miscible solvents such as THF, 1,4-dioxane, acetonitrile, DMF,1-methyl-2-pyrrolidinone, dimethoxyethane, ethyl acetate, C₁₋₄ alcoholssuch as methanol, ethanol, 1-propanol, isopropanol, n-butanol, andsec-butanol, and combinations thereof. Preferably, the organic solventis a C₁₋₄ alcohol, or C₁₋₄ alcoholacetonitrile mixture, and morepreferably, the alcohol is selected from 1-propanol and ethanol.Although the amount of water in the aqueous-organic solvent mixture maybe varied, preferably the volume percent of water in the mixture is 15percent or less, and more preferably 5 percent or less.

About 1 to 3 molar equivalents of the acid per molar equivalent of theracemic piperazine derivative are advantageously used in this procedure,and it is preferable to form the bis-acid salt.(1S)-(+)-10-Camphorsulfonic acid and (L)-pyroglutamic acid are thepreferred acids, and (L)-pyroglutamic acid is most preferred.

The temperatures at which steps (b) and (c) are performed may be variedaccording to techniques known to those skilled in the art. Generally, atemperature sufficient to dissolve any solids is all that is needed forstep (b), and may, e.g., be in the range of about 70° C. to the refluxtemperature of the solvent used. The heated solution should be allowedto cool slowly, preferably of its own accord, down to ambienttemperature, and may be further cooled to about 20°-23° C. for step (c).Optionally, the solution may be seeded with the appropriate salt ofeither (S) or (R)-2-tert-butylcarboxamidepiperazine to promotecrystallization.

After separating the crystalline precipitate from the mother liquor, itcan be determined whether the precipitate contains predominantly the Ror the S-antipode by standard techniques known in the art, such as achiral HPLC assay. "Predominantly" is intended to mean an enantiomericexcess (ee) of 90% or greater. The S-antipode can then be recovered fromthe precipitate or the mother liquor accordingly. For example, when theCSA salt is prepared, the S-antipode crystallizes out of solution;however, when the L-PGA salt is formed, the S-antipode remains in themother liquor and the R-antipode crystallizes out.

The processes and intermediates of this invention are useful for thepreparation of end-product compounds that are useful in the inhibitionof HIV protease, the prevention or treatment of infection by the humanimmunodeficiency virus (HIV), and the treatment of consequentpathological conditions such as AIDS. Treating AIDS or preventing ortreating infection by HIV is defined as including, but not limited to,treating a wide range of states of HIV infection: AIDS, ARC (AIDSrelated complex), both symptomatic and asymptomatic, and actual orpotential exposure to HIV. For example, the end-product compounds thatcan be made from the processes and intermediates of this invention areuseful in treating infection by HIV after suspected past exposure to HIVby, e.g., blood transfusion, organ transplant, exchange of body fluids,bites, accidental needle stick, or exposure to patient blood duringsurgery.

The end-product HIV protease inhibitors are also useful in thepreparation and execution of screening assays for antiviral compounds.For example, end-product compounds are useful for isolating enzymemutants, which are excellent screening tools for more powerful antiviralcompounds. Furthermore, such compounds are useful in establishing ordetermining the binding site of other antivirals to HIV protease, e.g.,by competitive inhibition. Thus the end-product compounds that are madefrom the processes and intermediates of this invention are commercialproducts to be sold for these purposes.

HIV protease inhibitor compounds that can be made from the intermediatesand processes of the instant invention are disclosed in EPO 541,164. TheHIV protease inhibitory compounds may be administered to patients inneed of such treatment in pharmaceutical compositions comprising apharmaceutical carrier and therapeutically-effective amounts of thecompound or a pharmaceutically acceptable salt thereof. EPO 541,164discloses suitable pharmaceutical formulations, administration routes,salt forms and dosages for the compounds.

The compounds of the present invention, may have asymmetric centers andoccur as racemates, racemic mixtures and as individual diastereomers, orenantiomers with all isomeric forms being included in the presentinvention.

When any variable (e.g., aryl, heterocycle, R, R¹, R², n, X, etc.)occurs more than one time in any constituent or in formulas I-VIII, itsdefinition on each occurrence is independent of its definition at everyother occurrence. Also, combinations of substituents and/or variablesare permissible only if such combinations result in stable compounds.

As used herein except where noted, "alkyl" is intended to include bothbranched- and straight-chain saturated aliphatic hydrocarbon groupshaving the specified number of carbon atoms (Me is methyl, Et is ethyl,Pr is propyl, Bu is butyl; t-Bu is tert-butyl); "alkoxy" represents analkyl group of indicated number of carbon atoms attached through anoxygen bridge; and "cycloalkyl" is intended to include saturated ringgroups, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl (Cyh)and cycloheptyl. "Alkenyl" is intended to include hydrocarbon groups ofeither a straight or branched configuration with one or morecarbon-carbon double bonds which may occur in any stable point along thechain, such as ethenyl, propenyl, butenyl, pentenyl, and the like."Alkynyl" is intended to include hydrocarbon groups of either a straightor branched configuration with one or more carbon-carbon triple bondswhich may occur in any stable point along the chain, such as ethynyl,propynyl, butynyl, pentynyl, and the like. "Halo", as used herein, meansfluoro, chloro, bromo and iodo. As used herein, "aryl" is intended tomean phenyl (Ph) or naphthyl.

The term heterocycle or heterocyclic, as used herein except where noted,represents a stable 5- to 7-membered mono- or bicyclic or stable 7- to10-membered bicyclic heterocyclic ring system any ring of which may besaturated or unsaturated, and which consists of carbon atoms and fromone to three heteroatoms selected from the group consisting of N, O andS, and wherein the nitrogen and sulfur heteroatoms may optionally beoxidized, and the nitrogen heteroatom may optionally be quaternized, andincluding any bicyclic group in which any of the above-definedheterocyclic rings is fused to a benzene ting. The heterocyclic ring maybe attached at any heteroatom or carbon atom which results in thecreation of a stable structure. Examples of such heterocyclic elementsinclude piperidinyl, piperazinyl, 2-oxopiperazinyl, 2-oxopiperidinyl,2-oxopyrrolodinyl, 2-oxoazepinyl, azepinyl, pyrrolyl, 4-piperidonyl,pyrrolidinyl, pyrazolyl, pyrazolidinyl, imidazolyl, imidazolinyl,imidazolidinyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, oxazolyl,oxazolidinyl, isoxazolyl, isoxazolidinyl, morpholinyl, thiazolyl,thiazolidinyl, isothiazolyl, quinuclidinyl, isothiazolidinyl, indolyl,quinolinyl, isoquinnolinyl, benzimidazolyl, thiadiazoyl, benzopyranyl,benzothiazolyl, benzoxazolyl, furyl, tetrahydrofuryl, tetrahydropyranyl,thienyl, benzothienyl, thiamorpholinyl, thiarnorpholinyl sulfoxide,thiamorpholinyl sulfone, and oxadiazolyl. Morpholino is the same asmorpholinyl.

Representative experimental procedures utilizing the novel process aredetailed below. These procedures are exemplary only and should not beconstrued as being limitations on the novel process of this invention.

EXAMPLE 1 ##STR25##

A solution of (-)-cis-1-aminoindan-2-ol 11 (884 g, 5.93 mol) in 17.8 Lof dry THF (KF=55 mg/mL) and triethylamine (868 mL, 6.22 mol) in a 50 Lround bottom flask equipped with a thermocouple probe, mechanicalstirrer, and a nitrogen inlet adapter and bubbler, was cooled to 15° C.Then, 3-phenylpropionyl chloride (1000 g, 5.93 mol) was added over 75minutes, while the internal temperature was maintained between 14°-24°C. with an ice-water cooling batch. After the addition, the mixture wasaged at 18° to 20° C. for 30 minutes and checked by HPLC analysis forthe disappearance of 11.

Progress of the reaction is monitored by high performance liquidchromatography (HPLC) analysis: 25 cm Dupont C8-RX column, 60:40acetonitrile/10 mM (KH₂ PO₄ /K₂ HPO₄), 1.0 mL/min., injection volume=20mL, detection=200 nm, sample preparation=500 X dilution. Approximateretention times:

    ______________________________________                                        retention time (min.)                                                                             identity                                                  ______________________________________                                        4.1                 hydroxy amide                                             6.3                 cis-amminoindanol                                         ______________________________________                                    

The reaction was treated with pyridinium p-toluenesulfonate (24 1 g,0.96 mol, 0.16 equiv.) and stirred for 10 minutes (the pH of the mixtureafter diluting 1 mL sample with an equal volume of water is between4.3-4.6). Then, 2-methoxypropene (1.27 L, 13.24 mol, 2.2 equiv.) wasadded and reaction was heated to 38°-40° C. for 2 h. The reactionmixture was cooled to 20° C. and partitioned with ethyl acetate (12 L)and 5% aqueous NaHCO₃ (10 L). The mixture was agitated and the layerswere separated. The ethyl acetate extract was washed with 5% aqueousNaHCO₃ (10 L) and water (4 L). The ethyl acetate extract was dried byatmospheric distillation and solvent switched to cyclohexane (totalvolume of ˜30L). At the end of the distillation and concentration (20volume % of ethyl acetate extraction volume), the hot cyclohexanesolution was allowed to slowly cool to 25° C. to crystallize theproduct. The resulting slurry was further cooled to 10° C. and aged for1 h. The product was isolated by filtration and the wet cake was washedwith cold (10° C.) cyclohexane (2×800 mL). The washed cake was driedunder vacuum (26" of Hg) at 40° C. to afford 1.65 kg of acetonide 7(86.4%, 98 area % by HPLC), ¹ H NMR (300.13 MHz, CDCl₃, major rotamer)δ7.36-7.14 (m, 9 H), 5.03 (d, J=4.4, 1 H), 4.66 (m, 1 H) 3.15 (m, 2 H),3.06 (br s, 2 H), 2.97 (m, 2 H), 1.62 (s, 3 H), 1.37 (s, 3 H); ¹³ C NMR(75.5 MHz, CDCl₃, major rotamer) δ_(c) 168.8, 140.9, 140.8, 140.6,128.6, 128.5, 128.4, 127.1, 126.3, 125.8, 124.1, 96.5, 78.6, 65.9, 38.4,36.2, 31.9, 26.5, 24.1. Anal. Calcd for C₂₁ H₂₃ NO₂ : C, 78.47; H, 7.21;N, 4.36. Found: C, 78.65; H, 7.24; N, 4.40.

EXAMPLE 2

    ______________________________________                                        Pyrazine-2-tert-butyl carboxamide 13                                           ##STR26##                                                                    ______________________________________                                        2-Pyrazinecarboxylic acid (12)                                                                      3.35 kg (27 mol)                                        Oxalyl chloride       3.46 kg (27.2 mol)                                      tert-Butylamine (KF = 460 μg/ml)                                                                 9.36 L (89 mol)                                         EtOAc (KF = 56 μg/ml)                                                                            27 L                                                    DMF                   120 mL                                                  1-Propanol            30 L                                                    ______________________________________                                    

The carboxylic acid 12 was suspended in 27 L of EtOAc and 120 mL of DMFin a 72 L 3-neck flask with mechanical stirring under N₂ and thesuspension was cooled to 2° C. The oxalyl chloride was added,maintaining the temperature between 5° and 8° C.

The addition was completed in 5 h. During the exothermic addition CO andCO₂ were evolved. The HCl that was formed remained largely in solution.A precipitate was present which is probably the HCl salt of the pyrazineacid chloride. Assay of the acid chloride formation was carded out byquenching an anhydrous sample of the reaction with t-butylamine. Atcompletion <0.7% of acid 12 remained.

The assay for completion of the acid chloride formation is importantbecause incomplete reaction leads to formation of a bis-tert-butyloxamide impurity.

The reaction can be monitored by HPLC: 25 cm Dupont Zorbax RXC8 columnwith 1 mL/min flow and detection at 250 nm; linear gradient from 98% of0.1% aqueous H₃ PO₄ and 2% CH₃ CN to 50% aqueous H₃ PO₄ and 50% CH₃ CNat 30 min. Retention times: acid 12=10.7 min, amide 13=28.1 min.

The reaction mixture was aged at 5° C. for 1 h. The resulting slurry wascooled to 0° C. and the tert-butylamine was added at such a rate as tokeep the internal temperature below 20° C.

The addition required 6 h, as the reaction was very exothermic. A smallportion of the generated tert-butyl-ammonium hydrochloride was swept outof the reaction as a fluffy white solid.

The mixture was aged at 18° C. for an additional 30 min. Theprecipitated ammonium salts were removed by filtration. The filter cakewas washed with 12 L of EtOAc. The combined organic phases were washedwith 6 L of a 3% NaHCO₃ and 2×2 L of saturated aq. NaCl. The organicphase was treated with 200 g of Darco G60 carbon and filtered throughSolka Flok and the cake was washed with 4 L of EtOAc. Carbon treatmentefficiently removed some purple color in the product.

The EtOAc solution of 13 was concentrated at 10 mbar to 25% of theoriginal volume. 30 L of 1-propanol were added, and the distillation wascontinued until a final volume of 20 L was reached.

At this point, the EtOAc was below the limit of detection in the ¹ H NMR(<1%). The internal temperature in this solvent change was <30° C. A1-propanol/EtOAC solution of 13 was stable to reflux at atmosphericpressure for several days.

Evaporation of an aliquot gave a tan solid m.p 87°-88° C.; ¹³ C NMR (75MHz, CDCl₃, ppm) 161.8, 146.8, 145.0, 143.8, 142.1, 51.0, 28.5.

EXAMPLE 3 ##STR27## Materials

Pyrazine-2-tert-butylcarboxamide 13 (2.4 kg, 13.4 mol) in 1-Propanolsolution 12 L 20% Pd(OH)₂ /C 16 wt. % water 144 g.

The pyrazine-2-tert-butylcarboxamide 13/1-propanol solution was placedinto the 5 gal autoclave. The catalyst was added and the mixture washydrogenated at 65° C. at 40 psi (3 atm) of H₂.

After 24 h. the reaction had taken up the theoretical amount of hydrogenand GC indicated <1% of 13. The mixture was cooled, purged with N₂ andthe catalyst was removed by filtration through Solka Floc. The catalystwas washed with 2 L of warm 1-propanol.

It was found that the use of warm 1-propanol during washing of thefilter cake improved filtration and lowered the losses of product on thefilter cake.

The reaction was monitored by GC (gas chromatography): 30 m Megaborecolumn, from 100° C. to 160° C. at 10° C./min, hold 5 min, then at 10°C./min to 250° C., retention times: 13=7.0 min, 14=9.4 min. The reactioncould also be monitored by TLC (thin layer chromatography) withEtOAc/MeOH (50:50) as solvent and Ninhydrin as developing agent.

Evaporation of an aliquot indicated that the yield over amidation andhydrogenation is 88% and that the concentration of 14 is 133 g/L.

Evaporation of an aliquot gave 14 as a whim solid m.p. 150°-151° C.; ¹³C NMR (75 MHz, D₂ O, ppm) 173.5, 59.8, 52.0, 48.7, 45.0, 44.8, 28.7.

EXAMPLE 4

    ______________________________________                                        (S)-2-tert-Butyl-carboxamide-piperazine bis (S)-Camphorsulfonic               acid salt (S)-15                                                               ##STR28##                                                                    Materials                                                                     ______________________________________                                        rac-2-tert-Butyl-carboxamide-piperazine 14                                                           4.10 kg (22.12 mol)                                    in 1-Propanol Solution in 25.5 Kg solvent                                     (S)-(+)-10-Camphorsulfonic acid                                                                      10.0 Kg (43.2 mol)                                     1-Propanol             12 L                                                   Acetonitrile           39 L                                                   Water                  2.4 L                                                  ______________________________________                                    

The solution of amine 14 in 1-propanol was charged to a 100 L flask withan attached batch concentrator. The solution was concentrated at 10 mbarand a temperature <25° C. to a volume of ca 12 L.

At this point the product had precipitated from the solution, but wentback into a solution when the mixture was heated to 50° C.

Analysis of a homogeneous aliquot indicated that the concentration of 14was 341 g/L The concentration was determined by HPLC: 25 cm DupontZorbax RXC8 column with 1.5 mL/min flow and detection at 210 nm,isocratic (98/2) CH₃ CN/0.1% aqueous H₃ PO₄. Retention time of 14: 2.5min.

Acetonitrile (39 L) and water (2.4 L) were added to give a clear,slightly brown solution.

Determination of the water content by KF titration and CH₃ CN/1-propanolratio by ¹ H NMR integration showed that the CH₃ CN/1-propanol/H₂ Oratio was 26/8/1.6. The concentration in the solution was 72.2 g/L.

The (S)-10-camphorsulfonic acid was charged over 30 min in 4 portions at20° C. The temperature rose to 40° C. after the CSA was added. After afew minutes a thick white precipitate formed. The whim slurry was heatedto 76° C. to dissolve all the solids, the slightly brown solution wasthen allowed to cool to 21° C. over 8 h.

The product precipitated at 62° C. The product was filtered withoutaging at 21° C., and the filter cake was washed with 5 L of the CH₃CN/1-propanol/H₂ O 26/8/1.6 solvent mixture. It was dried at 35° C. inthe vacuum oven with N₂ bleed to give 5.6 Kg (39%) of 15 as a whitecrystalline solid m.p 288°-290° C. (with decomp.) [α]_(D) ²⁵ =18.9°(c=0.37, H₂ O). ¹³ C NMR (75 MHz, D₂ O, ppm) 222.0, 164.0, 59.3, 54.9,53.3, 49.0, 48.1, 43.6, 43.5, 43.1, 40.6, 40.4, 28.5, 27.2, 25.4, 19.9,19.8.

The enantiomeric excess (ee) of the material was 95% according to thefollowing chiral HPLC assay: an aliquot of 15 (33 mg) was suspended in 4mL of EtOH and 1 mL of Et₃ N. Boc₂ O (11 mg) was added and the reactionmixture was allowed to age for 1 h. The solvent was completely removedin vacuo, and the residue was dissolved in ca. 1 mL of EtOAc andfiltered through a Pasteur piper with SiO₂, using EtOAc as eluent. Theevaporated product fractions were redissolved in hexanes at ca. 1 mg/mL.The enantiomers were separated on a Daicel Chiracell AS column with ahexane/IPA (97:3) solvent system at a flow rate of 1 mL/min anddetection at 228 nm. Retention times: S antipore=7.4 min, R=9.7 min.

EXAMPLE 5

    ______________________________________                                        (S)-2-tert-Butylcarboxamide-4-tert-butoxycarbonyl-piperazine 1                from salt 15                                                                   ##STR29##                                                                    Materials                                                                     ______________________________________                                        (S)-2-tert-Butyl-carboxamide-piperazine                                       Bis (S) - (+) - CSA salt 15, 95% ee                                                                 5.54 Kg (8.53 mol)                                      Di-tert-butyl dicarbonate                                                                           1.86 Kg (8.53 mol)                                      Lacamas                                                                       Et.sub.3 N            5.95 L (42.6 mol)                                       Aldrich                                                                       EtOH Punctilious 200 proof                                                                          55 L                                                    EtOAc                 2 L                                                     ______________________________________                                    

To the (S)-CSA salt 22 in a 100 L 3-neck flask with an addition funnelunder N₂ was added EtOH, followed by triethylamine at 25° C. The soliddissolved readily on the addition of the Et₃ N. The Boc₂ O was dissolvedin EtOAc and charged to the addition funnel. The solution of Boc₂ O inEtOAc was added at such a rate as to keep the temperature below 25° C.The addition took 3 h. The reaction mixture was aged for 1 h aftercompletion of the addition of the Boc₂ O solution.

The reaction can be monitored by HPLC: 25 cm Dupont Zorbax RXC8 columnwith 1 mL/min flow and detection at 228 nm, isocratic (50/50) CH₃CN/0.1M KH₂ PO₄ adjusted to pH=6.8 with NaOH. Retention time of 1=7.2min. The chiral assay was carried out using the same system as in theprevious step. The reaction could also be monitored by TLC with a 100%EtOAc as the solvent. (Rf=0.7)

The solution was then concentrated to ca. 10 L at an internaltemperature of <20° C. in a batch-type concentrator under 10 mbarvacuum. The solvent switch was completed by slowly bleeding in 20 L ofEtOAc and reconcentrating to ca 10 L. The reaction mixture was washedinto an extractor with 60 L of EtOAc. The organic phase was washed with16 L of 5% aqueous Na₂ CO₃ solution, 2×10 L Di water and 2×6 L ofsaturated aqueous sodium chloride. The combined aqueous washes were backextracted with 20 L of EtOAc and the organic phase was washed with 2×3 Lwater and 2×4 L of saturated aqueous sodium chloride. The combined EtOAcextracts were concentrated under 10 mbar vacuum with an internaltemperature of <20° C. in a 100 L batch-type concentrator to ca. 8 L.The solvent switch to cyclohexane was achieved by slowly bleeding in ca.20 L of cyclohexane, and reconcentrating to ca. 8 L. To the slurry wasadded 5 L of cyclohexane and 280 mL of EtOAc and the mixture was heatedto reflux, when everything went into solution. The solution was cooledand seed (10 g) was added at 58° C. The slurry was cooled to 22° C. in 4h and the product was isolated by filtration after a 1 h age at 22° C.The filter cake was washed with 1.8 L of cyclohexane and dried in thevacuum oven at 35° C. under N₂ bleed to give 1.87 Kg (77%, >99.9 area %by HPLC, R-isomer below level of detection) of 1 as a slightly tanpowder. [α]_(D) ²⁵ =22.0° (c=0.20, MeOH), m.p 107° C.; ¹³ C NMR (75 MHz,CDCl₃, ppm) 170.1, 154.5, 79.8, 58.7, 50.6, 46.6, 43.6, 43.4, 28.6,28.3.

EXAMPLE 6

    ______________________________________                                        (S)-2-tert-Butyl-carboxamide-piperazine bis (L)-Pyroglutamic                  acid 16                                                                        ##STR30##                                                                    Materials                                                                     ______________________________________                                        rac-2-tert-butyl-carboxamide-piperazine 14                                                          (0.11 mol)                                              in 1-propanol solution                                                                              155 ml, assay = 21.1 g                                  L-pyroglutamic acid   28 g, (0.21 mol)                                        Water                 5 ml                                                    ______________________________________                                    

The solution of racemic-2-tert-butyl-carboxamide-piperazine 14 in1-propanol was charged to a 500 ml round bottom flask with a refluxcondenser, mechanical stirrer and a nitrogen inlet. Water was addedalong with L-pyroglutamic acid and the resulting slurry was heated toreflux. The homogeneous yellow solution was cooled to 50° C. and seededwith the bis-(L)-PGA salt of the R amine (50 mgs). Solids began formingimmediately. The solution was further cooled to 25° C. and aged for 16hours. The solids were filtered at 22° C., and the filter cake waswashed with 35 ml cold 1-propanol/1% water. The filter cake was dried at35° C. in the vacuum oven with N₂ bleed to give 23.74 gms (48%) of(R)-2-tert-butyl-carboxamide-piperazine bis (L)-pyroglutamic acid. Theee of the material was 98% according to the chiral HPLC assay describedpreviously. The yellow mother liquors contained 22.6 gms (46%) of(S)-2-tert-butyl-carboxamide-piperazine bis (L)-pyroglutamic acid salt16 and the ee was 95% according to the chiral HPLC assay. The motherliquors were evaporated and used directly in the protection step.

    ______________________________________                                        (S)-2-tert-butylcarboxamide-4-tert-butoxycarbonyl-piperazine 1                from (S)-2-tert-butyl-carboxamide-piperazine bis (L)-pyroglutamic             acid salt 16                                                                   ##STR31##                                                                    Materials                                                                     ______________________________________                                        (S)-2-tert-butyl-carboxamide-piperazine                                       Bis (L)-pyroglutamic acid salt, 95% ee                                                              22.6 g (50.1 mmol)                                      Di-tert-butyl dicarbonate                                                                           11.1 g (50.1 mmol)                                      Et.sub.3 N            35.5 mL (0.254 mol)                                     1-Propanol            226 ml                                                  EtOAc                 24 ml                                                   ______________________________________                                    

To (S)-2-tert-butyl-carboxamide-piperazine bis (L)-pyroglutamic acidsalt in a 500 ml 3-neck flask with addition funnel under N₂ was added1-propanol. The gummy yellow solid dissolved readily on the addition ofthe Et₃ N. A solution of Boc₂ O in EtOAc was added over 2 h at 22° C.The reaction mixture was aged for 1 h after completion of the addition.

The reaction could be monitored by HPLC (high performance liquidchromatography) and TLC using the same procedures as for the conversionof 15 to 1

The solution was then concentrated and solvent switched to ethyl acetate(200 ml). The reaction mixture was washed with 50 ml of 7% aqueous Na₂CO₃ solution, 2×30 ml water and dried (Na₂ SO₄) and filtered. The EtOAcsolution was concentrated and solvent switched to cyclohexane (60 ml).EtOAc (1 mL) was added and the mixture was heated to reflux to dissolveall solids. The mixture was cooled and seeded (50 mg) at 52° C. Theslurry was cooled to 22° C. over 2 h and the product was isolated byfiltration after a 1 h age at 22° C. The filter cake was washed with 8ml of cyclohexane and dried in the vacuum oven at 35° C. under N₂ bleedto give 10.8 gms (74%, >99.9 area % by HPLC analysis, R-isomer belowlevel of detection) of 1 as an off white powder.

EXAMPLE 71-((R)-2',3'-Epoxypropyl)-(S)-2-tert-butylcarboxamide-4-tert-butoxycarbonyl-piperazine3

    ______________________________________                                         ##STR32##                                                                     ##STR33##                                                                    Materials                                                                     ______________________________________                                        (S)-2-tert-butylcarboxamide-                                                                        11.0 g (38.4 mmol)                                      4-tert-butoxycarbonyl-piperazine 1                                            (2S)-(+)-Glycidyl-3-nitrobenzenesulfonate                                                           9.96 g (38.4 mmol)                                      Diisopropylethylamine 5.5 mL (42.2 mmol)                                      DMF                   38 mL                                                   ______________________________________                                    

Piperazine 1 and (2S)-(+)-Glycidyl-3-nitrobenzenesulfonate 2 weredissolved in a 250 mL flask with magnetic stirring under N₂ in DMF andDIEA. The resulting homogenous solution was heated to 60°-62° C. for 9h.

TLC (100% EtOAc as eluent, Ninhydrin stain) indicated completeconsumption of piperazine 1.

The reaction was quenched by the addition of 30 mL of a 5% aqueousNaHCO₃ solution. The reaction mixture was extracted with 400 mL ofisopropyl acetate. The organic phase was washed with water (3×50 mL) andbrine (1×50 mL), dried (Na₂ SO₄) and evaporated to s give a yellow oil.Flash chromatography (4 cm×20 cm column, SiO2, gradient elution with30:70 EtOAc:hexanes to 60:40 EtOAc:hexanes) and evaporation of theproduct containing fractions gave 9.24 g (71% yield) of 3 as anoil:.[α]_(D) ²⁵ =-17.7° (c=0.12, MeOH); ¹³ C NMR (100 MHz, CDCl₃, -25°C., ppm of major rotamer) 170.0, 154.1, 80.2, 66.7, 56.3, 51.7, 50.8,50.2, 47.0, 44.0, 41.9, 28.3, 28.1.

EXAMPLE 8 ##STR34##

The piperazine 1 (2.00 g, 7.00 mmol) and (S)-glycidol 4 (930 μL, 14.0mmol) were heated at reflux in 19 mL of isopropanol for 17 h, then themixture was partitioned with 100 mL of ethyl acetate and 50 mL of water.The layers were separated, and the ethyl acetate layer was washed withsaturated sodium chloride, dried with MgSO₄, and concentrated to 2.4 gof a gum. A portion of the gum (241 mg) was treated with 2 mL ofpyridine and p-toluenesulfonyl chloride (130 mg, 0.68 mmol) overnight,then it was concentrated to an oil. The oil was partitioned with 25 mLof ethyl acetate and 10 mL of water. The ethyl acetate layer was washedwith brine, dried (MgSO4) and concentrated to an oil. The crude oil wasdissolved in 2 mL of THF and treated with 100 mg of 60% NaH dispersionin oil. After 1 h, the mixture was partitioned with ethyl acetate (50mL), and 10 mL of water. The ethyl acetate layer was dried with MgSO₄and concentrated to afford the desired epoxide 3 (see previousexperimental for spectral data).

EXAMPLE 9 ##STR35##

A solution of acetonide 7 (216 mg, 0.67 mmol) and N-Boc-piperazineepoxide 3 (229 g, 0.67 mmol, 1.0 equiv.) in 3.5 mL of THF (KF=22 μg/mL)(KF stands for Karl Fisher titration for water) in a 100 mL round bottomflask, equipped with a thermocouple, magnetic stirrer, and undernitrogen atmosphere, was cooled to -78° C. Then, n-butyllithium inhexanes solution (0.9 mL, 1.6M, 2.1 equiv.) was added, while keeping theinternal temperature between -78° C. to -73° C. The reaction mixture wasstirred at -76° C. for 1 h and then allowed to warm to -25° C. over 1 h.The mixture was stirred between -25° to -22° C. for 2.5 h. Then, thereaction mixture was quenched with DI water (5 mL) at -15° C. andpartitioned with ethyl acetate (20 mL). The mixture was agitated and thelayers were separated. The ethyl acetate extract was washed withsaturated NaCl (10 mL) and concentrated under reduced pressure (28" ofHg) to afford crude product which was chromatographed on a silica gelcolumn with ethyl acetate/hexane (3:2) to give the coupled product 8 (84mg, 20%) as a pale yellow syrup: ¹³ C NMR (CDCl₃, 75.4 MHz) δ172.6,170.2, 154.6, 140.8, 140.4, 139.6, 129.5, 128.8, 128.1, 127.2, 126.8,125.6, 124.1, 96.7, 80.4, 79.2, 65.9, 65.8, 62.2, 51.3, 50.1, 45.3,43.5, 39.5, 39.1, 36.2, 28.8, 28.4, 26.5, 24.2.

EXAMPLE 10 ##STR36##

To a solution of compound 8 (5.79 g. 8.73 mmol) in 25.5 mL isopropanolat 0° C. was added 20 ml of 6N aqueous HCl, then 15 minutes later 10 mLof concentrated HCl was added. After 1 hour, the mixture was warmed to20° C. and aged for 4 hours. The mixture was then cooled to 0° C., andthe pH was adjusted to 12.5 with 13 mL of 50% aqueous NaOH, whilekeeping the temperature ≦29° C. The mixture was extracted with 2×80 mLof EtOAc, and the extracts were dried with MgSO₄ and concentrated toafford 5.46 g of the product 9 as a colorless foam: ¹³ C NMR (75.4 MHz,CDCl₃) δ175.2, 170.5, 140.8, 140.5, 139.9, 129.1, 128.5, 127.9, 126.8,126.5, 125.2, 124.2, 73.0, 66.0, 64.8, 62.2, 57.5, 49.5, 47.9, 46.4,45.3, 39.6, 39.3, 38.2, 28.9.

EXAMPLE 11 ##STR37##

To the solution of 9 in EtOAc (10.5 L, KF=10 mg/mL) from the previousstep was charged with 20 L of sieve dried DMF (KF <30 mg/L) and themixture was heated with a steam bath under vacuum of 30" of Hg todistill off mainly water and/or any residual isopropanol or ethylacetate solvent. The final concentrate volume was 13.5 L (KF=1.8 mg/mL)and then triethylamine (2.86 L, 20.51 mol) was added to the 25° C.solution followed by 3-picolyl chloride hydrochloride (96%, 1287 g, 7.84mol). The resulting slurry was heated to 68° C.

The progress of the reaction was followed by HPLC analysis using thesame conditions as the previous step. Approximate retention times:

    ______________________________________                                        Retention time (min.)                                                                             Identity                                                  ______________________________________                                        2.7                 DMF                                                       4.2                 3-picolpl chloride                                        4.8                 L-735,524                                                 9.1                 penultimate 9                                             ______________________________________                                    

The mixture was aged at 68° C. until the residual penultimate compound 9was <0.3 area % by HPLC analysis. HPLC conditions: 25 cm Dupont C8-RXcolumn, 60:40 acetonitrile/10 mM (KH₂ PO₄ /K₂ HPO₄), 1.0 ml/min,detection=220 nm.

The mixture was stirred at 68° C. for 4 h, then cooled to 25° C. andpartitioned with ethyl acetate (80 L) and a mixture of 24 L of saturatedaqueous NaHCO₃ and distilled water (14 L). The mixture was agitated at55° C. and the layers were separated. The ethyl acetate layer was washedthree times with water (20 L) at 55° C. The washed ethyl acetate layeris concentrated at atmospheric pressure to a final pot volume of 30 L.At the end of the atmospheric concentration, water (560 mL) was added tothe hot solution and the mixture was cooled to 55° C. and seeded withL-735,524 monohydrate. The mixture was cooled to 4° C. and filtered tocollect the product. The product was washed with cold ethyl acetate (2×3L), and dried at house vacuum at 25° C. to afford 2905 g (70.7 %) ofL-735,524 as a white solid.

EXAMPLE 12

    ______________________________________                                        Kinetic Resolution of (S/R)-2-tert-Butylcarboxamide-4-tert-                   butoxy-carbonyl-piperazine 17 to 1                                             ##STR38##                                                                    Materials                                                                     ______________________________________                                        Crude (S/R)-2-tert-Butylcarboxamide-4-tert-                                                              1.40 g                                             butoxycarbonyl-piperazine 17                                                  (S)-2-tert-Butylcarboxamide-4-tert-butoxycarbonyl-                                                       4 × 0.14 g                                   piperazine 1 (>99.5% ee)                                                      Methylcyclohexane with 2% (vol/vol) EtOAc                                                                14 mL                                              ______________________________________                                    

The crude, gummy 17 is dissolved in 14 mL of the solvent mixture byheating to 90° C. The solution is allowed to cool, and at 10° C.intervals the solution is seeded with 0.14 g of 1 (>99.5% ee). At 55° C.the fourth 0.14 g batch of seed does not dissolve any more and onfurther slow cooling to room temperature a white crystalline mass forms.The reaction mixture is filtered, washed with 3 mL of themethylcyclohexane/EtOAc solvent mixture and dried in the vacuum ovenunder N₂ bleed to give 0.95 g of a white solid. Determination of theenantiomeric purity with a Chiracell AS column shows 93%ee.

EXAMPLE 13 ##STR39##

To a solution of 4-pyridine carboxaldehyde (36.7 mL, 0.384 mol) andmalonic acid (40 g, 0.384 mol) in 31 mL of pyridine was added piperdine(0.12 mL) and the mixture was warmed to 100° C. Caution: large volumesof CO₂ evolved. After 0.5 h, the reaction was cooled to room temperature(RT) and the solution solidified. This was triturated with 240 mL ofwater and filtered, and washed with 2×50 mL portions of water. The solidwas dried overnight at 42° C. under vacuum (10 mm Hg) to provide 37.1 gof a white solid; mp 295°-297° C.

EXAMPLE 14 ##STR40##

To a suspension of trans-3-(4-pyridyl)acrylic acid (10.0 g, 0.067 mol)in 500 mL of THF was added triethylamine (10.29 mL, 0.0738 mol) and thesolution was cooled to 0° C. Trimethylacetyl chloride (8.68 mL, 0.0704mol) was added and the reaction stirred for 0.5 h.2(R)-hydroxy-1(S)-indane (10.0 g, 0.067 mol) dissolved in 260 mL of THFwas added via cannula. After 2 h the reaction was warmed to RT andstirred an additional 15 h. The solvent was removed in vacuo and theresulting solid was triturated with cold ethyl acetate (150 mL) andfiltered. This was dried overnight under vacuum (0.5 mm of Hg) toprovide 18.5 g of a white solid; mp 205°-207° C.

EXAMPLE 15 ##STR41##

To a suspension of N-(2(R)-hydroxy-1(S)-indanyl)-trans-3-(4-pyridyl)acrylamide (18.5 g, 0.066 mol) in 700 mL of methylene chloride was addeddimethoxypropane (49.0 mL, 0.402 mol) followed by (+/-) camphorsulphonic acid (46.8 g, 0.201 mol). After 20 minutes the reaction becamehomogeneous. The reaction mixture stirred for 3 h and was washed withsaturated NaHCO₃ (2×150 mL). The aqueous layer was extracted withmethylene chloride (3×200 mL) and the combined organic layer was driedover MgSO₄, filtered and concentrated to an oil. Purification by flashcolumn chromatography (100×150 mm column of silica gel; gradient elution1:30:69, 2:30:68, 3:30:67, 5:30:65 MeOH:CHCl₃ saturated with NH₃ : CH₂Cl₂)provided 16.0 g of a white foam. (Rf 0.46 in 5:30:65 MeOH:CHCl₃saturated with NH₃ : CH₂ Cl₂)

EXAMPLE 16 ##STR42##

ToN-(1,2-N,O-isopropylidenen-2(R)-hydroxy-1(S)-indanyl)-trans-3-(4-pyridyl)acrylamide(16.0 g, 0.0499 mol) dissolved in ethanol (200 mL) and THF (200 mL) wasadded 14.0 g Pd(OH)₂ on carbon (20% by weight). The flask was thencharged with H₂ and stirred 9 h. The solution was purged with Ar,filtered through a plug of celite and washed with ethanol (100 mL). Thesolvent was removed in vacuo and the product was purified via flashcolumn chromatography (100×150 mm column of silica gel; gradient elution1:30:69, 2:30:68, 3:30:67, 5:30:65 MeOH:CHCl₃ saturated with NH₃ : CH₂Cl₂) which provided 13.8 g of a white foam. (Rf 0.5 in 5:30:65MeOH:CHCl₃ saturated with NH₃ : CH₂ Cl₂)

EXAMPLE 17 ##STR43##

Using substantially the same procedure as for the preparation ofN-(2(R)-hydroxy-1(S)-indanyl)-trans-3-(4-pyridyl) acrylamide, butsubstituting the appropriate starting materials, the title compound wasprepared. Physical data: mp 119-120, Analysis Calculated for C₁₇ H₁₆ N₂O₂ ·0.65H₂ O: C, 69.92; H, 5.97; N, 9.59. Found: C, 69.94; H, 5.74, N,9.84.

EXAMPLE 18 ##STR44##

Using substantially the same procedure as for the preparation ofN-(1,2-N,O-isopropylidenen-2(R)-hydroxy-1(S)-indanyl)-trans-3-(4-pyridyl)acrylamide,but substituting the appropriate starting material, the title compoundwas prepared. Physical data: mp 134-136, Analysis Calculated for C₂₀ H₂₀N₂ O₂ ·0.25H₂ O: C, 73.94; H, 6.36; N, 8.62. Found: C, 73.95; H, 6.18,N, 8.70.

EXAMPLE 19 ##STR45##

Using substantially the same procedure as for the preparation ofN-(1,2-N,O-isopropylidenen-2(R)-hydroxy-1(S)-indanyl)-3-(4-pyridyl)propylamide,but substituting the appropriate starting material, the title compoundwas prepared.

While the foregoing specification teaches the principles of the presentinvention, with examples provided for the purpose of illustration, itwill be understood that the practice of the invention encompasses all ofthe usual variations, adaptations, and modifications, as come within thescope of the following claims and its equivalents.

What is claimed is:
 1. A compound of formula ##STR46##